The enthalpy changes of salting process of hen-egg
white lysozyme in buffer acetate solutions (pH=4.25) as a function of concentration
of following electrolytes: LiCl, KCl, K2SO4,
Li2 SO4 and (NH4)2SO4
are determined. Obtained data according to McMillan and Mayer’s approach,
has been analyzed in the terms of the enthalpic pairwise interaction coefficients:
lysozyme – lysozyme hxx,
and lysozyme – salt hxy.
The ability of cations to precipitate lysozyme solution in relation to the
concentration of cations can be seen from the series as follows: Li+>
Authors:X. Zielenkiewicz, G. Perlovich, and M. Wszelaka-Rylik
A new device, based on the inert gas flow method, for measuring the vapour pressure and the determination of the enthalpy of sublimation in a wide range of temperatures (up to 573 K) is described in this paper. The limits of the flow rate as important experimental parameter were determined for the given instrument. The results of calibration showed a good precision and reproducibility of the measurements of the enthalpy of sublimation. The results of the determination of some derivatives of pyrimidine were presented.
Authors:W. Zielenkiewicz, I. Terekhova, M. Wszelaka-Rylik, and R. Kumeev
Calorimetry, densimetry, 1H NMR and UV–vis spectroscopy were used to characterize inclusion complex formation of hydroxypropylated α- and β-cyclodextrins
with meta- and para-aminobenzoic acids in aqueous solutions at 298.15 K. Formation of more stable inclusion complexes between para-aminobenzoic acid and cyclodextrins was observed. The binding of aminobenzoic acids with hydroxypropyl-α-cyclodextrin was
found to be enthalpy-governed owing to the prevalence of van der Waals interactions and possible H-binding. Complex formation
of hydroxypropyl-β-cyclodextrin with both acids is mainly entropy driven. The increased entropy contribution observed in this
case is determined by dehydration of solutes occurring during the revealed deeper insertion of aminobenzoic acids into the
cavity of hydroxypropyl-β-cyclodextrin. By comparing complex formation of aminobenzoic acids with native and substituted cyclodextrins
it was found that the availability of hydroxypropyl groups slightly influenced the thermodynamic parameters and did not change
the binding mode or driving forces of interaction.